Full stack development refers to the practice of developing both the front-end and back-end of a website or application. This includes everything from the user interface and design to the server-side logic and database management.

Full stack developers are responsible for the entire development process of a website or application, from the initial planning and design phases to the final deployment and maintenance. They have a deep understanding of both the front-end and back-end technologies, and are able to build complete, functional web systems from start to finish.

There are many different technologies and frameworks that full stack developers can use to build websites and applications. Some of the most popular ones include:

1. HTML: HTML (HyperText Markup Language) is a standard markup language used to create web pages. It provides the structure and content of a webpage, and is the foundation of all web development.
2. CSS: CSS (Cascading Style Sheets) is a style sheet language used to describe the look and formatting of a document written in HTML. It allows developers to control the appearance of a webpage, including colors, fonts, and layout.
3. JavaScript: JavaScript is a programming language that is commonly used to add interactivity and dynamic behavior to web pages. It can be used to create interactive elements such as forms, menus, and games, and is an essential part of modern web development.
4. jQuery: jQuery is a fast, small, and feature-rich JavaScript library that simplifies HTML document traversing, event handling, and animation. It is widely used to add interactivity to websites and is often used in conjunction with other technologies such as CSS and HTML.
5. Bootstrap: Bootstrap is a popular front-end framework that provides a set of ready-made styles and layout options for web development. It allows developers to create responsive, mobile-first websites quickly and easily, and is widely used for building modern, professional-looking websites.
6. React: React is a popular JavaScript library for building user interfaces. It allows developers to create reusable components that can be easily managed and updated, and is often used for building complex, interactive web applications.
7. Angular: Angular is a comprehensive JavaScript framework for building web applications. It provides a set of tools and libraries for building front-end and back-end functionality, and is often used for building large, scalable web applications.
8. Vue: Vue is a progressive JavaScript framework for building web applications. It is lightweight and easy to learn, and is often used for building smaller, single-page applications.
9. Ruby on Rails: Ruby on Rails is a popular back-end framework for building web applications. It is based on the Ruby programming language and provides a set of tools and libraries for building server-side functionality, including database management and security.
10. Django: Django is a high-level Python web framework that encourages rapid development and clean, pragmatic design. It is often used for building complex, data-driven websites and applications.

These are just a few examples of the many technologies and frameworks that full stack developers can use to build web systems. The choice of which ones to use often depends on the specific requirements of the project and the preferences of the developer.

Full stack development can be a challenging and rewarding career path, as it requires a wide range of skills and a deep understanding of both front-end and back-end technologies. It is a constantly evolving field, with new technologies and frameworks emerging all the time. To be successful, full stack developers must be willing to continuously learn and adapt.

There are several ways that full stack developers can earn an income:

1. Full-time employment: Many full stack developers work full-time for a company or organization, either as an employee or as a contractor. This can involve working on a variety of projects, including building and maintaining websites and applications for the company or its clients.
2. Freelancing: Full stack developers can also earn an income by working as freelancers, taking on projects from a variety of clients on a project-by-project basis. This can involve working remotely or on-site, and can offer a high degree of flexibility and freedom.
3. Consulting: Full stack developers can also offer their expertise to clients on a consulting basis, providing guidance and support on web development projects. This can involve working on a project-by-project basis or providing ongoing support and maintenance.
4. Entrepreneurship: Full stack developers can also start their own business, either as a solo entrepreneur or as part of a team. This can involve building and selling web-based products or services, or offering web development services to clients.

The income of a full stack developer can vary widely depending on factors such as their level of experience, the type of work they are doing, and the location in which they are working. In general, full stack developers with a strong portfolio of work and a proven track record of success can command higher rates and have more opportunities for earning an income.